Beta-Amyloid Peptide 1-42-Conjugated Magnetic Nanoparticles For The Isolation And Purification Of Glycoproteins In Egg White

A beta(1-42)-conjugated magnetic nanoparticles, A beta(1-42)@MNP, were prepared by covalently coupling A beta(1-42) to hyperbranched polyethyleneimine (PEI)-modified magnetic nanoparticles via N-(3dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC). A beta(1-42)'s high binding capacity to glycosyl groups facilitates A beta(1-42)@ MNP composite to be a promising selective adsorbent for glycoproteins in egg whites. In our study, under conditions of pH 4.0, the adsorption efficiency of A beta(1-42)@MNP composite for ovalbumin (100 mu g mL(-1)) was 98.4% and its maximum adsorption capacity was 344.8 mg g(-1); under the condition of pH 4.0 and 200 mmol L-1 NaCl, its adsorption efficiencies for ovalbumin and ovotransferrin were 96.9% and 60.0%, respectively. According to these primary data, in practice, ovalbumin was removed from egg white by A beta(1-42)@MNP composite at pH 4.0 (step I), and then after adding NaCl until the final salt concentration reached 200 mmol L-1 (pretreated egg white), we utilized the same adsorbent to further isolate/purify glycoproteins (step II). SDS-PAGE results showed that A beta(1-42)@MNP composite could largely remove ovalbumin in step I and could isolate/purify the remaining ovalbumin and ovotransferrin in step II. LC-MS/MS analysis results showed that the removal of ovalbumin reduced its percentage in egg white samples from 32.93% to 11.05% in step I and the remaining ovalbumin and ovotransferrin were enriched in step II, where the final percentage reached 11.6% and 12.6%, respectively. In summary, 81 protein species were identified after two-step extraction with A beta(1-42)@MNP on egg white, while only 46 protein species were identified directly from raw egg white without any pretreatment. This work well illustrates the excellent adsorption performance of A beta(1-42)@MNP composite to glycoproteins and its potential in the application of proteomic studies on low-abundance proteins in egg white.